Axis labeller for unit-cell charts

A thin wrapper around scales::label_number() anchored to a cell_size: divides each axis break by cell_size and formats the result. Use with scale_*_continuous(labels = ...) when the corresponding geom_unit_*() layer was given a non-default cell_size and you want the axis to read in cell counts (or in a natural-unit scale like thousands / millions, via suffix).

Because label_cells() is a wrapper, every option that scales::label_number() accepts (accuracy, big.mark, decimal.mark, scale_cut, style_positive, ...) is available via ....

Usage

label_cells(cell_size = 1, prefix = "", suffix = "", ...)

Arguments

cell_size

The same cell_size value passed to geom_unit_bar() / geom_unit_col() / geom_unit_histogram(). Must be a positive finite scalar. Translated internally to scale = 1 / cell_size.

prefix, suffix

Character strings to wrap each label. Default "" (no decoration). Useful when cell_size matches a natural unit – e.g. cell_size = 1e3 with suffix = "k" produces "1k", "2k", ...; cell_size = 1e6 with suffix = "M" produces "1M", "3M", ...

...

Other arguments forwarded to scales::label_number() – e.g. accuracy = 0.1, big.mark = ",", scale_cut = scales::cut_short_scale() (auto SI prefix).

Value

A function suitable for the labels argument of ggplot2::scale_y_continuous() / ggplot2::scale_x_continuous().

See also

scales::label_number() for the underlying formatter and the full list of forwardable options; geom_unit_bar() for the geoms that consume cell_size.

Examples

library(ggplot2)

# cell_size = 1,000 -> axis reads "1k", "2k", ... (one cell = 1,000)
df_k <- data.frame(x = c("A", "B", "C"), y = c(4000, 11000, 8000))
ggplot(df_k, aes(x, y)) +
  geom_unit_col(cell_size = 1e3) +
  scale_y_continuous(labels = label_cells(1e3, suffix = "k")) +
  labs(
    x = NULL,
    y = NULL,
    caption = "One cell equals 1,000 observations.") +
  coord_equal(ratio = 1 / 1e3)


# cell_size = 1,000,000 -> axis reads "1M", "3M", ... (one cell = 1,000,000)
# Flipped orientation: bars run along x, baselines on y.
df_M <- data.frame(x = c("A", "B", "C"), y = c(2.4e6, 1.1e6, 3.8e6))
ggplot(df_M, aes(y = x, x = y)) +
  geom_unit_col(cell_size = 1e6) +
  scale_x_continuous(labels = label_cells(1e6, suffix = "M")) +
  labs(
    x = NULL,
    y = NULL,
    caption = "One cell equals 1,000,000 observations.") +
  coord_equal(ratio = 1e6)